Hemorrhage and edema in acute spinal cord compression: demonstration by MR imaging

Until the development of magnetic resonance (MR) imaging there was no nondestructive technique for monitoring the pathologic response to acute spinal cord trauma. The characteristic findings of hemorrhage, necrosis, and edema have been well described in animal models. We used a 1.4-T, animal imaging system to study acute cord contusions in rats. Contusions were induced by means of extradural aneurysm clip compression, and imaging was performed 3-5 hours after injury with short and long spin-echo (SE) sequences. Animals were killed immediately after imaging, and the gross anatomic and histologic findings were correlated with image appearances. On long SE sequences edema appeared as an area of high signal intensity that extended proximal and distal to the site of contusion. At the contusion site there was focal intraparenchymal hemorrhage which had low signal intensity on T2-weighted images, presumably owing to deoxyhemoglobin. MR imaging can be used to assess pathologic changes resulting from acute cord contusion and to aid in differentiating irreversible damage (hemorrhage) from potentially reversible edema.